// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/trace_event/heap_profiler_allocation_register.h"

#include <stddef.h>
#include <sys/mman.h>
#include <unistd.h>

#include "base/bits.h"
#include "base/logging.h"
#include "base/process/process_metrics.h"

#ifndef MAP_ANONYMOUS
#define MAP_ANONYMOUS MAP_ANON
#endif

namespace base {
namespace trace_event {
    namespace internal {

        namespace {
            size_t GetGuardSize()
            {
                return GetPageSize();
            }
        }

        void* AllocateGuardedVirtualMemory(size_t size)
        {
            size = bits::Align(size, GetPageSize());

            // Add space for a guard page at the end.
            size_t map_size = size + GetGuardSize();

            void* addr = mmap(nullptr, map_size, PROT_READ | PROT_WRITE,
                MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

            PCHECK(addr != MAP_FAILED);

            // Mark the last page of the allocated address space as inaccessible
            // (PROT_NONE). The read/write accessible space is still at least |min_size|
            // bytes.
            void* guard_addr = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(addr) + size);
            int result = mprotect(guard_addr, GetGuardSize(), PROT_NONE);
            PCHECK(result == 0);

            return addr;
        }

        void FreeGuardedVirtualMemory(void* address, size_t allocated_size)
        {
            size_t size = bits::Align(allocated_size, GetPageSize()) + GetGuardSize();
            munmap(address, size);
        }

    } // namespace internal
} // namespace trace_event
} // namespace base
